This invention relates to a web rewind apparatus having a cutless web transfer unit and particularly having a cutless web transfer unit for separating of a web from a rewinding roll and transferring of the separated web onto a new rotating rewinding core.
Web material is formed in relatively large rolls for subsequent processing and converting. The web may be a paper, film or other thin flexible material which is manufactured as a continuous web wound onto a suitable supporting roll form. Various converting and processing machines are constructed with an unwind stage for receiving of the web roll. The web is threaded and passes through the converting machine which has one or more work stations for treating and processing of the web as it moves therethrough. The integrity of the web is often maintained and rewound at a rewind station for subsequent handling. The rewound roll may be of a similar or different size from that of the original roll. Further, the system is normally established to permit a continuous run by the automated insertion of a supply roll at the unwind station and automatic interconnection and splicing to the existing roll, in combination with a similar automatic transfer from a fully rewound roll to a new rewinding core unit. The automated roll interchange and splicing at the unwind stand is well known. Similarly, the automatic transfer of the processed web in the rewind stand and the transfer of a full roll to a new rewinding core unit is also well known.
Generally, the rewind stand in commercial apparatus includes a turret mechanism for automated movement of a full rewound roll unit to a load/unload station, with the simultaneous movement of a new roll unit to a rewind station. In an adhesiveless transfer, a knife cut-off and special web transfer mechanism is provided at the rewind station for cutting of the web at that location and transferring of the cut web onto the new roll unit. The tail end of the web on the fully wound roll is wound onto such roll to form a final rewound roll at the load/unload station. The severing of the web and the transfer onto the new core unit has presented a continuing design consideration particularly with the increasing linear web speeds in web processing or converting machines. For example, current converting machines having a specification of 2,500 feet per minute or more is considered a highly desirable feature in the paper converting art.
Both coreless and core rewinding apparatus is used. In one typical core rewind apparatus, a turret is provided having core supporting arms projecting diametrically through the axis of rotation. The axially extended arms terminate in axially aligned chucks for releasably engaging the opposite ends of an elongated tubular core. Individual drive motors are coupled to each of the core supports and generally are mounted to provide direct drive of the core spindles. In addition, a separate turret drive provides for controlled and selective rotation of the turret between 180.degree. horizontal orientations. The load/unload station is located to one side of the turret and one set of the core spindle assembly is located at the load/unload station. The rewind station is located to the diametrically opposite side of the turret and the opposite core spindle assembly is located at the web transfer rewind station. The free end of the web is wound on the core at the rewind station. After a couple of turns, the free end of the web is captured to the core and the rotation of the core continues to pull the web onto the core to rewind the web into a new rewound roll. Conventionally, a rider roll is mounted at the rewind station to established a pressurized interengagement of the web onto the roll or the core and also to iron out air entrapped between the wound layers of the web. A tension control means is also incorporated into the drive system to maintain a predetermined web tension on the web as it rewound onto the roll. When the roll has reached a desired diameter, the rider roll is removed from its operative position. The turret is then rotated with a continuing rewind of the web onto the essentially filled rewound roll. A guide roll is provided in the turret mechanism to raise the web and permit continuous movement onto the roll as the turret rotates. Simultaneously, the new core assembly or unit, which was inserted at the load/unload station, rotates into the position for winding of the web onto the new core. The transfer unit generally includes an enlongated knife extending across the web. The knife is movably mounted to the outside face of the web which moves and slightly downstream of the core location in the rewind station. The knife is adapted to move downwardly onto the moving web between the new core in the rewind station and the essentially fully wound roll at the unload station. The knife thus functions to define a tail end of the web on the rewound roll and a free unsupported end of the web to be transferred onto the new core at the rewind station. The movement of the tail end has not presented a significant problem. The transfer of the free, unsupported end of the web onto the new core has required special and relatively complex equipment. Generally, in adhesiveless transfers in addition to the knife, various air directing and guide mechanisms have been provided for capture of the free web end and directing it onto the core to initiate a couple of wraps after which the rotation of the core insures the firm grip on the free end of the web for continuous rewinding and initiation of a new rewound roll. For example, various suggestions have provided various forms of air transfer with air blasts applied to the outer side of the web immediately adjacent to the knife to force the web onto the core at least during the initial wraps. In addition, various guide and shields are provided to guide the web directly or in combination with the air transfer to maintain the web onto the roll core during the initial rotations and wrapping of the free end of the web onto the core. The above system particularly describes an adhesiveless transfer. Adhesive transfers are also used in the art wherein an adhesive or tape medium is applied to the core to receive and capture the free end of the web.
Reference may be made to the following prior art patents which disclose various knife and associated devices for cutting and transfer of the web:
______________________________________ Patent No. Issue Date ______________________________________ 3,148,843 09-15-1964 3,744,730 07-10-1973 3,765,615 10-16-1973 3,871,595 03-18-1975 4,033,521 07-05-1977 4,345,722 08-24-1982 4,422,586 12-27-1983 4,431,140 02-14-1984 4,445,646 05-01-1984 4,515,321 05-07-1985 4,529,141 07-16-1985 4,546,930 10-15-1985 4,489,900 12-25-1984 ______________________________________
Although such systems are relatively widely used, the inventor has found that prior art systems are complex, expensive and subject to less than optimum repeatable operation. Further, the mechanisms are particularly troublesome when attempting to effect a transfer at and above web speeds of 2,500 feet per minute. Although knife mechanisms can be provided to provide the relatively instaneous severing, the subsequent movement of the free end of the web onto the core in a reliable and repeatable manner has not been found to be established by commercially available mechanisms or the mechanisms suggested in the prior art. The knife must generally sever the web at a rate faster than the web speed and even though the knife may provide proper severing, the mechanical mechanisms and the air flows created with air transfer and similar systems, particularly at high speed, cannot provide a totally repetitive sequence such as to insure a similar transfer of a free web end onto the core with a reliable multiple initial wraps to secure the web to the core. Thus the free end of the web is subject to various conditions which tend to vary the movement somewhat. In addition, the air flow and its interaction with the mechanical mechanism may well constitute a source of variation in web transfer, resulting in unsuitable and unexceptable transfer.
In addition, the combination of the knife, the air mechanism and the various shields and guides add significantly to the initial cost of the rewind apparatus. Such complex mechanisms also must of course be periodically serviced and maintained, further contributing to the total operating cost of the paper converting machinery.
In summary, the prior art with its various suggestions provides at best a less than satisfactory web transfer mechanism for use with rewind apparatus and add an undesirable initial and subsequent operating cost, particularly as the web speed increases. There is therefore a need for an inproved reliable transfer mechanism which will provide an effective, reliable and repeatable transfer and preferably at a lesser initial and subsequent operational cost.